Rock bit with a thermal insulating seal ring positioned in the seal gland

ABSTRACT

A rock bit includes a shaft and a cone mounted for rotation about the shaft at a journal bearing. A seal gland for the rock bit is defined at least by the shaft and the cone. A compressible seal ring is positioned within the seal gland. A thermal insulating ring is installed within the seal gland and positioned between the compressible seal ring itself and the journal bearing to insulate the compressible seal ring from heat radiating from the journal bearing.

PRIORITY CLAIM

The present application is a continuation of U.S. patent applicationSer. No. 12/252,252 filed Oct. 15, 2008, which claims the benefit ofU.S. Provisional Application for Patent 60/984,635 filed Nov. 1, 2007entitled “Rock Bit With A Seal Thermal Insulating Ring”, the disclosuresof which are hereby incorporated by reference to the maximum extentallowable by law.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to earth boring bits, and moreparticularly to those having rotatable cutters, also known as cones.

2. Description of Related Art

Reference is made to U.S. Pat. No. 3,397,928 to Galle, the disclosure ofwhich is hereby incorporated by reference. Reference is still furthermade to U.S. Pat. No. 3,765,495 to Murdoch, the disclosure of which ishereby incorporated by reference.

Earth boring bits with rolling element cutters have bearings employingeither rollers as the load carrying element or with a journal as theload carrying element. The use of a sealing means in rock bit bearingshas dramatically increased bearing life in the past fifty years.

Early seals for rock bits were designed with a metallic Bellevillespring clad with an elastomer, usually nitrile rubber (NBR). Themetallic spring provided the energizing force for the sealing surface,and the rubber coating sealed against the metal surface of the head andcone and provided a seal on relatively rough surfaces because thecompliant behavior of the rubber coating filled in the microscopicasperities on the sealing surface. Belleville seals of this type wereemployed mainly in rock bits with roller bearings. The seal would faildue to wear of the elastomer after a relatively short number of hours inoperation, resulting in loss of the lubricant contained within thebearing cavity. The bit would continue to function for some period oftime utilizing the roller bearings without benefit of the lubricant.

A significant advancement in rock bit seals came when o-ring type sealswere introduced. These seals, as disclosed by Galle, were composed ofnitrile rubber and were circular in cross section. The seal was fittedinto a radial gland formed by cylindrical surfaces between the head andcone bearings, and the annulus formed was smaller than the originaldimension as measured as the cross section of the seal. The squeeze ofthe seal was defined as the percentage reduction of the cross sectionfrom its original state to the compressed state. Murdoch disclosed avariation of this seal by elongating the radial dimension which, whencompared to the seal disclosed by Galle, required less percentagesqueeze to form an effective seal. This was referred to in the art as ahigh aspect ratio seal. Several other minor variations of this concepthave been used, each relying on an elastomer seal squeezed radially in agland formed by cylindrical surfaces between the two bearing elements.

Over time, the rock bit industry has moved from a standard nitrilematerial for the seal ring, to a highly saturated nitrile elastomer foradded stability of properties such as thermal resistance and chemicalresistance.

Reference is now made to FIG. 1 which illustrates a prior artconfiguration for an earth boring bit. FIG. 2 illustrates a close-upview of the prior art configuration focusing on the area of the sealingsystem 2 and journal bearing 11 associated with a rotating cone 4 and ashaft 5 of the bit head 1. An o-ring seal 6 is squeezed between acylindrical cone sealing surface 9 and a cylindrical head sealingsurface 7. The term “cylindrical” in this context refers to a surfacethat is parallel to an axis of cone rotation. An inner radial conesurface 8 is provided on the grease side of the seal, while an outerradial head surface 10 is provided on the drilling fluid side of theseal. The term “radial” in this context refers to a surface extendingaway from the axis of cone rotation. In this illustrated implementation,the radial surfaces 8 and 10 are normal (i.e., perpendicular) to theaxis of cone rotation. It will be noted that the sealing pressure isbetween surfaces 7 and 9.

Reference is now made to FIG. 3 wherein there is shown another prior artseal. In this case the seal is a high aspect ratio seal. It will benoted that the seal 6 is squeezed between the cylindrical cone sealingsurface 9 and the cylindrical head sealing surface 7. An inner radial(normal) cone surface 8 is provided on the grease side of the seal,while an outer radial (normal) cone surface 10 is provided on thedrilling fluid side of the seal. The normal surfaces 8 and 10 arerequired to stabilize the seal (for example, prevent motion, buckling,twisting) when in operation. It will also be noted that surface 10 islocated on the cone 4 (not the head as in FIG. 2).

FIGS. 2 and 3 both illustrate the use of a journal bushing 12 positionedbetween the rotating cone 4 and the cantilever bearing shaft 5 in thearea of the journal bearing 11.

With the configurations illustrated in FIGS. 1, 2 and 3, the seal 6 isdirectly exposed to heat generated by the journal bearing 11 associatedwith the shaft 5 and rotating cone 4. Exposure to this heat duringoperation of the rock bit is known to change the mechanical propertiesof the elastomer used for the o-ring seal 6. A reduced seal life resultsfrom this heat exposure. A need exists to protect the o-ring seal fromthis heat exposure.

SUMMARY OF THE INVENTION

An insulating ring is provided in the seal gland to protect the sealfrom bearing generated heat.

In an embodiment, a ring shaped like a washer is inserted between theo-ring seal and the journal bearing to block or insulate the o-ring sealfrom heat generated by the journal bearing. This insulating washer isposition so as to rest against an inner (grease) side of the seal gland.More specifically, the insulating washer is positioned between theo-ring seal itself and the inner radial surface provided on the greaseside of the seal associated with the cone.

In an embodiment, the insulating ring is made of a rigid, insulatingmaterial such as a polyetheretherketone (PEEK), also referred to as apolyketone. Functionally-speaking, the insulating ring offers a thermalinsulation barrier positioned between the journal bearing (where heat isgenerated and radiates) and the seal. Heat transmission from the journalbearing to the seal is minimized (substantially reduced in comparison toimplementations lacking the insulating ring).

In an embodiment, a seal for a rock bit comprises: a gland including aninner radial surface; a sealing member installed within the gland; and athermal insulating member installed within the gland between the sealingmember itself and the inner radial surface.

In another embodiment, a seal for a rock bit comprises: an annular glanddefined in part by an inner radial surface associated with a cone memberof the rock bit; an o-ring seal positioned within the annular gland; anda thermal insulating ring installed within the annular gland andpositioned between the o-ring seal itself and the inner radial surfaceof the cone member.

In an embodiment, a rock bit comprises: a shaft; a cone mounted forrotation about the shaft at a journal bearing; a seal gland defined atleast by an inner radial surface; a compressible seal ring positioned inthe seal gland; and a thermal insulating ring installed within the sealgland and positioned between the compressible seal ring itself and theinner radial surface.

In another embodiment, a rock bit comprises: a shaft; a cone mounted forrotation about the shaft at a journal bearing; a seal gland defined bythe cone and shaft; a compressible seal ring positioned in the sealgland; and a thermal insulating ring installed within the seal gland andpositioned between the compressible seal ring itself and the journalbearing to insulate the compressible seal ring from heat radiating fromthe journal bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become clear in thedescription which follows of several non-limiting examples, withreferences to the attached drawings wherein:

FIG. 1 illustrates a prior art configuration for an earth boring bit;

FIG. 2 illustrates a close-up view of the prior art configuration ofFIG. 1 focusing on the area of the seal;

FIG. 3 illustrates another prior art seal configuration;

FIGS. 4-6 illustrate embodiments of a seal gland and journal bearingwith an insulating ring provided in the seal gland to protect the sealfrom journal bearing generated heat; and

FIGS. 7A and 7B illustrate plan and side edge views, respectively, ofthe insulating ring used in FIGS. 4-6.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is now made to FIG. 4 which illustrates an embodiment of aseal gland and journal bearing with an insulating ring provided in theseal gland to protect the seal from journal bearing generated heat. Theo-ring seal 6 is squeezed between a cylindrical cone sealing surface 9and a cylindrical head sealing surface 7. An inner radial surface 8 isprovided on the grease side of the seal 6, while an outer radial surface100 is provided on the drilling fluid side of the seal 6. The surfacesjust described generally define an annular gland 20 of a sealing systemlocated at the base of the shaft 5 between the leg of the bit and thejournal bearing 11.

An insulating ring 14 is positioned between the inner radial surface 8and the seal 6 on the grease side of the seal. With this position, theinsulating ring 14 is placed between the journal bearing 11 area and theseal 6 in order to protect the seal 6 from bearing generated heat.Functionally-speaking, the insulating ring 14 offers a thermalinsulation barrier positioned between the journal bearing 11 and theseal 6. Heat transmission or radiation from the journal bearing 11 tothe seal is minimized (substantially reduced in comparison toimplementations lacking the insulating ring 14). The insulating ring 14is washer-shaped comprised of a flat disk structure with a centralopening. An inner circumferential edge 22 of the ring 14 (associatedwith the central opening) is positioned adjacent the cylindrical headsealing surface 7, while an outer circumferential edge 24 of the ring 14is positioned adjacent the cylindrical cone sealing surface 9. Theopposed top and bottom surfaces 26 and 28 of the ring 14 are positionedadjacent the inner radial surface 8 and seal 6, respectively.

Reference is now made to FIG. 5 which illustrates another embodiment ofa seal gland and journal bearing with an insulating ring provided in theseal gland to protect the seal from journal bearing generated heat. Theo-ring seal 6 is squeezed between a cylindrical cone sealing surface 9and a cylindrical head sealing surface 7. An inner radial surface 8 isprovided on the grease side of the seal 6, while an outer radial surface100 is provided on the drilling fluid side of the seal 6. The surfacesjust described generally define an annular gland 20 of a sealing systemlocated at the base of the shaft 5 between the leg of the bit and thejournal bearing 11. The journal bearing 11 further includes a journalbushing 12 positioned between the rotating cone 4 and the cantileverbearing shaft 5.

An insulating ring 14 is positioned between the inner radial surface 8and the seal 6 on the grease side of the seal. With this position, theinsulating ring 14 is placed between the bushing 12 of the journalbearing 11 and the seal 6 in order to protect the seal 6 from bearinggenerated heat. Functionally-speaking, the insulating ring 14 offers athermal insulation barrier positioned between the journal bearing 11 andthe seal 6. Heat transmission or radiation from the journal bearing 11to the seal is minimized (substantially reduced in comparison toimplementations lacking the insulating ring 14). The insulating ring 14is washer-shaped comprised of a flat disk structure with a centralopening. An inner edge 22 of the ring 14 is positioned adjacent thecylindrical head sealing surface 7, while an outer edge 24 of the ring14 is positioned adjacent the cylindrical cone sealing surface 9. Theopposed top and bottom surfaces 26 and 28 of the ring 14 are positionedadjacent the inner radial surface 8 and seal 6, respectively. Stillfurther, in the illustrated implementation, the top surface 26 of thering 14 is also positioned adjacent a radial surface end 32 of thejournal bushing 12. It will be recognized that the journal bearing 11could alternatively have the configuration illustrated in FIG. 2, itwhich case the included ring 14 need not make contact with the includedjournal bushing 12.

Reference is now made to FIG. 6 which illustrates another embodiment ofa seal gland and journal bearing with an insulating ring provided in theseal gland to protect the seal from journal bearing generated heat. Thesealing system provides a high aspect ratio seal (see, also, FIG. 3).The seal 6 is squeezed between the cylindrical cone sealing surface 9and the cylindrical head sealing surface 7. An inner radial cone surface8 is provided on the grease side of the seal, while an outer radialsurface 10 is provided on the drilling fluid side of the seal. Thesurface 10 is located on the cone 4. The surfaces just describedgenerally define an annular gland 20 of a sealing system located at thebase of the shaft 5 between the leg of the bit and the journal bearing11. A journal bushing 12 is positioned between the head 4 and thecantilever bearing shaft 5 for the journal bearing 11.

An insulating ring 14 is positioned between the inner radial surface 8and the seal 6 on the grease side of the seal. With this position, theinsulating ring 14 is placed between the bushing 12 of the journalbearing 11 and the seal 6 in order to protect the seal 6 from bearinggenerated heat. Functionally-speaking, the insulating ring 14 offers athermal insulation barrier positioned between the journal bearing 11 andthe seal 6. Heat transmission or radiation from the journal bearing 11to the seal is minimized (substantially reduced in comparison toimplementations lacking the insulating ring 14). The insulating ring 14is washer-shaped comprised of a flat disk structure with a centralopening. An inner edge 22 of the ring 14 is positioned adjacent thecylindrical head sealing surface 7, while an outer edge 24 of the ring14 is positioned adjacent the cylindrical cone sealing surface 9. Theopposed top and bottom surfaces 26 and 28 of the ring 14 are positionedadjacent the inner radial surface 8 and seal 6, respectively.

Reference is now made to FIGS. 7A and 7B which illustrate a plan viewand a side edge view, respectively, of the insulating ring 14. Theinsulating ring 14 has a flat ring structure that is generally shapedlike a washer (such as a disk with a center hole). The width of the ringmember (from outer edge 24 to inner edge 22) generally conforms to beabout slightly less than a depth of the gland along the inner radialsurface 8. The outer diameter of the ring (defined by outer edge 24)generally conforms to be about slightly less than an outer diameter ofthe annular gland structure (defined by surface 9). The inner diameterof the ring (defined by inner edge 22) generally conforms to be aboutslightly more than an outer diameter of the shaft 5 (defined by surface7). The thickness of the ring is a matter of design choice for achievinga desired thermal insulating function within the confines andconstraints of the gland geometry and the selection of the materialsused to fabricate the ring. In one implementation, the thickness may beapproximately 0.031 inches, but a thicker or thinner ring 14 may be useddepending on the properties of the material chosen to make the ring andthe specific details of the installation such as gland geometry.

The insulating ring is preferably made of a rigid, insulating plasticmaterial such as a polyetheretherketone (PEEK), also referred to as apolyketone. It will be recognized that other insulating materials knownto those skilled in the art would also be suitable material choices foruse in fabricating the insulating ring. As an alternative to PEEK, thering may be made from polyphenylene sulfide (PPS), Glass/cloth PhenolicLaminates, and polyimide (Vespel®) and other like alternatives. Suchother materials considered for use in fabricating the insulating ringshould be highly resistant to thermal degradation, and resistant to bothorganic and aqueous environments. Materials of the kind known andordinarily used in bearings, piston parts, pumps, compressor platevalves, and cable insulation applications make suitable materialchoices.

It will be noted that the ring 14 includes a radial slit opening 38. Theslit 38 is present to allow for installation of the ring within thegland in some instances. The slit 38 further allows for some thermalexpansion of the ring to occur within the gland without fear of adeformation which would put pressure on the o-ring seal 6 and adverselyaffect wear of the o-ring seal. It will be noted that the slit 38 allowsfor assembly with minimal likelihood of damage to the ring. In thisregard the ring slit 38 is a convenient, but not required, option.

In any of the embodiments shown herein, as well as other installationsincluding a sealing annular gland of the type shown, it will be notedthat the insulating ring may be sized and shaped as needed to fit withinthe gland. That fit may in an embodiment be a loose fit which wouldallow the ring to rotate about the journal bearing 11 axis and withinthe gland. That fit may alternatively be a press fit within the gland sothat the ring rotates with cone 4 rotation. In another embodiment, thering may be attached to the inner radial surface 8 of the gland so as torotate with the cone.

Although preferred embodiments of the method and apparatus have beenillustrated in the accompanying Drawings and described in the foregoingDetailed Description, it will be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications and substitutions without departing fromthe spirit of the invention as set forth and defined by the followingclaims.

1. A seal for a rock bit, comprising: a gland in a cone of said rockbit, said gland including an inner radial surface and a cylindricalsurface; a sealing member installed within the gland and in sealingcontact with said cylindrical surface of said gland; and a non-sealingthermal insulating member installed within the gland between the sealingmember itself and the inner radial surface.
 2. The seal as in claim 1wherein the sealing member is an o-ring seal.
 3. The seal as in claim 1wherein the thermal insulating member covers at least substantially allof the inner radial surface of the gland.
 4. The seal as in claim 3wherein the thermal insulating member is made of a rigid, insulatingplastic material.
 5. The seal as in claim 3 wherein the thermalinsulating member is shaped like a washer.
 6. The seal as in claim 5wherein the washer-shaped thermal insulating member includes a radialslit opening.
 7. The seal as in claim 1 wherein the cone rotates about ajournal bearing, and wherein the thermal insulating member is installedbetween the sealing member itself and the journal bearing.
 8. The sealas in claim 5 wherein the thermal insulating member permits fluidcommunication between the gland and the journal bearing.
 9. The seal asin claim 1 wherein the cone rotates about a journal bearing, wherein thejournal bearing includes a journal bushing.
 10. The seal as in claim 9wherein the journal bushing includes a radial surface, and wherein thethermal insulating member covers all of the inner radial surface of thegland and at least substantially all of the radial surface of thejournal bushing.
 11. The seal as in claim 9 wherein the journal bushingincludes a radial surface, and wherein the thermal insulating memberdoes not cover any of the radial surface of the journal bushing.
 12. Theseal as in claim 9 wherein the journal bushing includes a radial surfacewhich is aligned with the inner radial surface of the gland.
 13. Theseal as in claim 1 wherein the thermal insulating member is attached tothe inner radial surface.
 14. The seal as in claim 1 wherein the thermalinsulating member touches the o-ring seal.
 15. The seal as in claim 1wherein the thermal insulating member is made of a laminated material.16. The seal as in claim 1 wherein the thermal insulating member is madeof a polyphenylene sulfide material.
 17. The seal as in claim 1 whereinthe thermal insulating member is made of a polyimide material.
 18. Theseal as in claim 1 wherein the gland is an annular gland defining a highaspect ratio sealing structure.
 19. The seal as in claim 1 wherein thethermal insulating member is made of a material selected from the groupconsisting of polyetheretherketone, polyphenylene sulfide, Glass/clothPhenolic Laminates, and polyimide.
 20. A rock bit, comprising: a shaft;a cone mounted for rotation about the shaft at a journal bearing; a sealgland defined at least by an inner radial surface; a compressible sealring positioned in the seal gland; and a non-sealing thermal insulatingring installed within the seal gland and positioned between thecompressible seal ring itself and the inner radial surface.
 21. The rockbit of claim 20 wherein the thermal insulating ring is installed betweenthe compressible seal ring itself and the journal bearing.
 22. The rockbit of claim 20 wherein the thermal insulating ring covers at leastsubstantially all of the inner radial surface of the gland.
 23. The rockbit of claim 20 wherein the thermal insulating ring insulates thecompressible seal ring from heat radiating from the journal bearing. 24.The rock bit of claim 23 wherein the thermal insulating ring is made ofa rigid, insulating plastic material.
 25. The rock bit of claim 20wherein the inner radial surface is a surface on the cone.
 26. The rockbit of claim 20 wherein the seal gland is an annular gland defining ahigh aspect ratio sealing structure.
 27. The rock bit of claim 20wherein the thermal insulating member is made of a material selectedfrom the group consisting of polyetheretherketone, polyphenylenesulfide, Glass/cloth Phenolic Laminates, and polyimide.
 28. A rock bitcomprising: a shaft; a cone mounted for rotation about the shaft at ajournal bearing; a seal gland defined at least by an inner radialsurface; a compressible seal ring positioned in the seal gland; and athermal insulating ring installed within the seal gland and positionedbetween the compressible seal ring itself and the inner radial surface;wherein the thermal insulating ring covers at least substantially all ofthe inner radial surface of the gland; wherein the journal bearingincludes a journal bushing, and wherein the thermal insulating ring isinstalled between the compressible seal ring itself and the journalbushing.
 29. The rock bit of claim 28 wherein the journal bushingincludes a radial surface, and wherein the thermal insulating ringcovers all of the inner radial surface of the seal gland and at leastsubstantially all of the radial surface of the journal bushing.
 30. Therock bit of claim 28 wherein the journal bushing includes a radialsurface, and wherein the thermal insulating ring does not cover any ofthe radial surface of the journal bushing.
 31. The rock bit of claim 28wherein the journal bushing includes a radial surface which is alignedwith the inner radial surface of the seal gland.
 32. The rock bit ofclaim 28 wherein the thermal insulating member permits fluidcommunication between the seal gland and the journal bearing.
 33. A rockbit comprising: a shaft; a cone mounted for rotation about the shaft ata journal bearing; a seal gland defined at least by an inner radialsurface; a compressible seal ring positioned in the seal gland; and athermal insulating ring installed within the seal gland and positionedbetween the compressible seal ring itself and the inner radial surface;wherein the thermal insulating ring covers at least substantially all ofthe inner radial surface of the gland; wherein the thermal insulatingring is shaped like a washer.
 34. The rock bit of claim 33 wherein thewasher-shaped thermal insulating ring includes a radial slit opening.35. A rock bit comprising: a shaft; a cone mounted for rotation aboutthe shaft at a journal bearing; a seal gland defined at least by aninner radial surface; a compressible seal ring positioned in the sealgland; and a thermal insulating ring installed within the seal gland andpositioned between the compressible seal ring itself and the innerradial surface; wherein the thermal insulating member is made of alaminated material.
 36. A rock bit comprising: a shaft; a cone mountedfor rotation about the shaft at a journal bearing; a seal gland definedat least by an inner radial surface; a compressible seal ring positionedin the seal gland; and a thermal insulating ring installed within theseal gland and positioned between the compressible seal ring itself andthe inner radial surface; wherein the thermal insulating member is madeof a polyphenylene sulfide material.
 37. A rock bit comprising: a shaft;a cone mounted for rotation about the shaft at a journal bearing; a sealgland defined at least by an inner radial surface; a compressible sealring positioned in the seal gland; and a thermal insulating ringinstalled within the seal gland and positioned between the compressibleseal ring itself and the inner radial surface; wherein the thermalinsulating member is made of a polyimide material.